Polycarbonates derived from reactions involving organic dihydroxy compounds and carbonic acid derivatives have found extensive commercial application because of their excellent mechanical and physical properties. These thermoplastic polymers are particularly suited for the manufacture of molded products where impact strength, rigidity, toughness, thermal stability, dimensional stability as well as excellent electrical properties are required.
In comparison with non-reinforced polycarbonates, glass fiber reinforced polycarbonates have both substantially increased flexural strength and stiffness and a substantially increased E-modulus, but have a decreased impact strength, notched impact strength and elongation at break. This decline in impact and other physical properties is thought to be attributable to the formation of stress concentrations in the vicinity of the individual glass fibers causing propagation of cracks in the molded articles. Improved properties of glass reinforced polycarbonate composites have been reported in U.S. Pat. Nos. 4,056,504; 4,147,707; 4,097,435 and 4,048,133 and in PCT/US79/00371. Polyanhydrides are reported as additives to molding compositions in U.S. Pat. No. 3,586,659 and as an ingredient of a cross-linked polyester in U.S. Pat. No. 3,732,337.
In accordance with the present invention, glass-fiber reinforced aromatic polycarbonates are provided featuring both an improved impact strength and a greater elongation at break.